1. Technical Field
The present invention relates to a flat panel display device and, more particularly, to an organic light emitting display (OLED) device in which an inorganic passivation layer is disposed under a pixel isolation layer, and a method of fabricating the same.
2. Related Art
Organic light emitting display (OLED) devices are self-emitting display devices which include a plurality of pixels arranged in a display region. Each pixel includes at least one switching transistor, a driving transistor, a capacitor and an EL device. The EL device includes an anode electrode, a cathode electrode, and an organic layer having a light emitting layer and interposed between the anode and cathode electrodes.
Organic light emitting display (OLED) devices are classified into bottom emitting OLED devices and top emitting OLED devices according to the direction of light emitted from the light emitting layer of an EL device in a pixel arranged in a pixel region. In a top emitting structure, light emitted from an organic light emitting layer of a pixel is extracted from the opposite direction to a TFT array substrate in which the pixel is arranged, and in a bottom emitting structure, light is extracted through a TFT array substrate in which the pixel is arranged. The top emitting structure has a higher aperture ratio than the bottom emitting structure.
Conventionally, an OLED device is fabricated by forming a thin film transistor, including a gate, a semiconductor layer and source/drain electrodes, on a substrate, forming a passivation layer and/or a planarization layer on the substrate including the thin film transistor, and forming an organic EL device, including an anode electrode, an organic light emitting layer, and a cathode electrode, on the passivation layer. The emission characteristics of the organic EL device, such as brightness and uniformity, deteriorate dramatically after the organic EL device is driven for a predetermined time, thereby decreasing reliability. Factors which decrease the reliability of the organic EL device may be moisture, oxygen, and other contaminants which permeate into the organic EL device.
A passivation layer is required under a sealing member to lengthen the lifetime of an organic EL device, and to prevent failure of a pad in OLED devices. In conventional OLED devices, a passivation layer is formed between a thin film transistor and an anode electrode, and an opening is formed to expose a pad. Accordingly, the process for manufacturing conventional OLED devices is complicated, since mask processes are needed to form an opening for the passivation layer and to form an opening for a pixel isolation layer.